In general, silicon carbide, boron carbide and silicon nitride are representative non-oxide materials and have mechanical characteristics, such as high strength, high hardness and wear-resistance characteristics as well as thermal characteristics, such as oxidation-resistance, corrosion-resistance, thermal shock resistance, and high-temperature strength characteristics.
Such non-oxide materials have the strong covalent bond, so the non-oxide materials must be subject to the sintering process under the specific condition, such as the high temperature condition, in order to process the non-oxide materials. The sintering process for the non-oxide materials includes the pressureless sintering, the reaction sintering, the recrystallization, the oxide bonding and the hot press sintering.
It is generally known in the art that the hot press sintering, in which pressure is applied under the high temperature condition, represents superior sintering characteristics. In a hot press sintering apparatus that performs the hot press sintering, a mold member, which may not be broken under the high temperature and high pressure, is required. In particular, since a metallic sintering aid is not added to provide high purity non-oxide material, the sintering process must be performed under the higher temperature and higher pressure condition with high purity member. Thus, the mold member must not be broken under the higher temperature and higher pressure condition.
The interior of the hot press sintering apparatus must be kept at a predetermined temperature to sufficiently heat the raw material such that the shape and the characteristics of the sintered material can be improved.
However, heat may be generated from parts connected to a press device in the hot press sintering apparatus. In this case, the characteristics of the sintered material, such as density of the sintered material, may deteriorate. This problem becomes severe when the sintered material having a relatively large size is manufactured.